(1) Field of the Invention
This invention relates to industrial ballistic tools, and more particularly to ammunition therefor.
(2) Description of the Related Art
Industrial ballistic tools are used in a variety of applications. One common application is the in situ cleaning of kilns, for which the tools are commonly identified as kiln guns. Additional applications lie in the tapping and cleaning of furnaces, the cleaning of copper smelters, the cleaning and clearing of silos, the cleaning of boilers, and the like.
By way of example, rotary kilns, which are used to calcine cement and lime, are typically 3 to 7 meters in diameter and 30 to 150 meters long. Calcining takes place at elevated temperatures, typically in the range of 1100° C. to 1500° C. During the calcining process, because of many processing variables, the product may adhere to the sidewall of the kiln forming a clinker, ring or dam. If this adherent obstruction is not removed, additional product will accumulate, reducing or stopping throughput. Removal of the obstruction is necessary.
It is not economically feasible to stop the kiln to remove the obstruction. Also, considering that the ring may form 5 to 10 meters from the end of the kiln, it is not safe or efficient for an operator to attempt to manually remove the obstruction with a long pole or by like methods. Thus many users of rotary kilns utilize industrial ballistic tools. A tool operator will position the tool in a kiln port and then fire metallic projectiles at the obstruction. Impact of the projectiles with the obstruction removes the obstruction from the sidewall of the kiln. The metallic projectiles are usually formed from lead, a dense material with a relatively low vaporization (boiling) temperature of 1750° C. The lead projectiles knock clinkers from the kiln sidewall and then fall into the kiln and may be vaporized.
Industrial ballistic tools are also utilized by manufacturers of steel, ferrosilicon and other materials. Prior to casting these metals, molten metal is typically contained within an electric furnace sealed by a carbon or clay base plug. Since the molten metal is at a temperature in excess of 2500° C., manual removal of the plug is not feasible. One way that the plug may be removed is with an industrial ballistic tool. A metallic projectile is fired from the industrial ballistic tool to break open the plug, starting the flow of molten metal. To prevent contamination of the metal, the projectile typically is formed of a material such as lead that will vaporize on contact with the molten metal after rupturing the plug.
Due to environmental concerns, lead is being phased out as a projectile material for use with industrial ballistic tools. Zinc and zinc alloys have also been utilized as lead substitutes. Their relatively low density may make them disadvantageous for certain uses. A ballistically stabilized zinc-based projectile is described in U.S. Pat. No. 5,824,944 of Jack D. Dippold et al.
Additionally, when repeated firing heats the tool chamber, the plastic tubes of many existing industrial shells may melt and/or leave a residue. The residue may deleteriously affect the firing of subsequent rounds.
In other fields, so-called “bulletless ammunition” has been developed. Cartridges without bullets or other substantial projectiles have been utilized as “blanks” or to propel grenades and the like. However, U.S. Pat. No. 3,621,781 discloses bulletless ammunition in which the sidewall of a spent cartridge becomes the projectile propelled by the charge of the subsequent cartridge. In the small arms field, substantial developments in such bulletless ammunition technology were made by Douglas Olson. These include use of cut down brass rifle cases as the case/projectile for use in revolvers and autoloaders. These are discussed in Karwan, C. Hollowpoint Bulletless Ammo, Hi-Tech Firearms, Petersen Publishing Co., (October, 1998), pp. 65–68.